What's the answer to question 1a and 1b regarding calculating the daily balance? I'm a little confused thanks
116 Chapter 5 ANALYZING DATA 5.1 How Does Acclimatization Affect Plant Energy Balance? Many plants can adjust their morphology and biochem- 40 istry to match the light conditions under which they are grown. The curves depicted in the figure are from 30 Olle Björkman's classic studies and show the net pho- tosynthetic CO, uptake for spearscale plants (Atriplex Grown in high-light conditions triangularis) grown under high-light (920 pumol/m2/s of photosynthetically active radiation) and low-light (92 Hmolu/m2/s) conditions. 1. Assuming no further physiological changes occur, cal 20 10 culate the daily carbon balance for leaves of the high- conditions: a. Plants are kept at a light level (irradiance) of 200 umol Grown in low-light conditions light and low-light plants grown under the following m2/s for 2 hours, then switched to an irradiance of 500 1,000 1,500 2,000 25 1,500 μmol/m2/s for 10 hours, then switched back to 200 μmol/m2/s for 2 hours. The lights are then turned off for 10 hours. (This light regime approximates Photosynthetically active irradiance (jamo!/m2/s) sunny conditions in an open subtropical savanna.) distinction in carbon balance under high-light condi- tions (calculated in part a of question 1)and low-light conditions (calculated in part b)? b. Plants are kept at an irradiance of 50 μmol/m2/s for 2 hours, then switched to an irradiance of 200 μmol/ m2/s for 10 hours, then switched back to 50 μmol/ might contribute to the differences in nighttime respiration rates? hours. (This light regime is similar to that expected in a tropical rainforest understory.) 2. High-light and low-light plants exhibit differences in maximum net photosynthesis rates, light compen- Björkman, O. 1981. Responses to different quantum flux densities In Physiological Plant Ecology Encyclopedia of Plant Physiology.OL Lange et al. leds). 57-101. Springer-Verlag. Berlin. sation points, and nighttime respiration. Which of See the companion website for a similar ANALYZING DATA exercise. these three differences contributes the most to the ycle is not operating, energy continues to accumulate in he light-harvesting arrays, and if enough energy builds p, it can damage the photosynthetic membranes. Plants ve evolved a number of ways of dissipating this energy afely, including the use of carotenoids to release it as of Arctic and alpine environments can photosyn t temperatures close to freezing, while desert plants have their highest photosynthetic rates at tempea that are hot enough to denature most other plants zymes (40°C-50°C or 104°F-122°F). Plants that acce tize to changes in temperature synthesize differen of photosynthetic enzymes with different tempera optima (Figure 5.9B). Temperature also influences th idity of the cell and organelle membrane 4.2). Cold sensitivity in plants of tropical and peratur eat, as described in Web Extension 5.1. Temperature influences photosynthesis in two mairn ways: through its effects on the rates of chemical reactions nd by influencing the structural integrity of membranes nd enzymes. Autotrophs acclimatize and adapt to tem- erature variation by changing properties of the Calvin cle enzymes and /or the photosynthetic membranes. ifferent photosynthetic organisms have different form ciated with loss of membra ty, which inhibits the functioning of the light-ha
